We plan to test these hypotheses by conducting a randomized, placebo-controlled, treatment trial of Chantix. Measures of CO levels in expired air (10 ppm or lower), self-reported abstinence, and psychopathology ratings will be used to evaluate primary and secondary outcomes along with safety assessments. Smoking abstinence is defined as 7-day point prevalence of self-reported no smoking verified objectively by expired CO levels of 10 ppm or less, and will be assessed at 12-weeks (or end of treatment phase) as the primary outcome. The same criterion will be used to assess maintenance of abstinence in the non-treatment phase, i.e. at 24 weeks or end of study.